High efficiency directional light source using lens optics

ABSTRACT

At least one embodiment in the disclosure describes a high efficiency directional light engine. The light engine comprises a light emitter emitting light and a collimation lens. The collimation lens has a cone-shaped sidewall, a base surface and a curved top surface. The height of the cone-shaped sidewall is at least three times more than the diameter of the base surface. The light emitter is optically coupled to and disposed in close proximity to the base surface. One or more first reflection images of the light emitter result from first reflection of the light off a surface of the cone-shaped sidewall. The diameter of the light emitter is substantially close to the diameter of the base surface so that the light emitter and the first reflection images form a virtual point light source with minimal gap(s) or without any gap between the light emitter and the first reflection images.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/559,063, filed on Nov. 12, 2011, which is incorporated herein byreference.

TECHNICAL FIELD

This invention relates to optical devices. In particular, this inventionrelates to an optical device to achieve directional light output with asmall optical beam divergence angle.

BACKGROUND

Lasers can be directional light sources. However, a laser is a coherentlight source, which is not suitable for general illuminationapplications due to its speckle property and single wavelengthcharacteristics. Incoherent light is usually not directional and thelight output has a very large angular dispersion. There are differentapproaches to achieve directional incoherent light sources withdirectional light output. One simple way is to use a focusing lens toconvert light from a point-like light source, such as an LED, into adirectional light beam. So far, most of the collimated light sources onthe market are achieved using this approach. However, such an approachcuts off side emission from the emitter, which dramatically lowers thelight intensity of the directional light output. There are alsoapproaches using non-imaging optics to achieve directional light output,such as parabolic mirrors, mirrors with special curvatures, etc.However, to achieve a small light output beam angle, the mirror used inthese approaches is of substantial size compared to the size of thelight emitter. Additionally, these approaches present mirrors surfacefabrication challenges, increasing the final product cost.

SUMMARY

At least one embodiment of the present invention discloses a new designand the fabrication method to make a high brightness, high efficiencydirectional light source, which has directional light output withcontrollable small beam divergence angle. Directional light source withsmall beam divergence is desired in many applications, including lightengines for projectors, stage spotlighting, long distance illumination,etc. Such directional light source can be fabricated using LEDs or otherproper light emitters.

In one embodiment, such directional light source is realized byintegrating a light emitter having a small light output surface area, acone-shaped mirror (also referred to as cone mirror) with a half-coneangle of no smaller than about 30°, and a focusing optical device, suchas a collimation lens. The light emitted from the light emitter entersand is collected by the cone mirror to form a directional light emissionpattern with a beam angle very close to the cone angle. The focusingoptical lens, then, is used to convert all of the light collected bycone mirror into a directional optical beam with desired small beamangle. Such design enables the collection of all light emitted from theemitter and the optical power loss during the concentration process isminimized. Thus, a high brightness, high efficiency directional lightsource can be fabricated. Also, the fabrication of such light source issimple and straightforward, which ensures a low-cost manufacture of suchdirectional light source.

In another embodiment, such directional light source is realized by alight engine integrating a light emitter with a collimation lens. Thecollimation lens has a cone-shaped sidewall, a base surface and a curvedtop surface. The height of the cone-shaped sidewall is at least threetimes more than the diameter of the base surface. The light emitter isoptically coupled to and disposed in close proximity to the basesurface. One or more first reflection images of the light emitter resultfrom first reflection of the light off a surface of the cone-shapedsidewall. The diameter of the light emitter is substantially close tothe diameter of the base surface so that the light emitter and the firstreflection images form a virtual point light source with minimal gap(s)or without any gap between the light emitter and the first reflectionimages.

The design enables the fabrication of directional light source usinglight emitters with small sizes, compared to conventional approaches.That will help to fabricate the directional light sources with smallsizes, which are desirable in the market.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages disclosedherein will be apparent from the following description of particularembodiments disclosed herein, as illustrated in the accompanyingdrawings in which like reference characters refer to the same partsthroughout the different views. The drawings are not necessarily toscale, emphasis instead being placed upon illustrating the principlesdisclosed herein.

FIG. 1 illustrates an example of a directional light source including alight emitter, a cone mirror and a focusing optical device.

FIG. 2A illustrates a cross-sectional view of a cone mirror with a lightemitter at a base opening of the cone mirror.

FIG. 2B illustrates example light rays emitted from the light emitter.

FIG. 2C illustrates example reflection images causes by reflection offthe cone mirror.

FIG. 2D illustrates a beam angle and a cone angle.

FIG. 3A illustrates an example of a directional light source with asmall beam angle.

FIG. 3B illustrates the relationship between the beam angle and thedimensions of a cone mirror and a light emitter of the directional lightsource.

FIG. 4A illustrates a cross-sectional view of an example of a conemirror.

FIG. 4B illustrates a cross-sectional view of a bottom half of the conemirror.

FIG. 5A illustrates an example of a flat light emitter.

FIG. 5B illustrates an example of a light emitter including a reflectivecup.

FIG. 5C illustrates an example of a light emitter including atransparent dome lens.

FIG. 5D illustrates an example of a light emitter including a lighttransmission device.

FIG. 5E illustrates an example of a light emitter having a circularemission area.

FIG. 5F illustrates an example of a light emitter having a squareemission area.

FIG. 6A illustrates an example of a square cross-sectional mirror withreflective inside surfaces.

FIG. 6B is a top view of the square cross-sectional mirror withreflective inside surfaces.

FIG. 6C illustrates a cross-sectional view of an example of a conemirror with square base opening and circular top opening.

FIG. 6D illustrates a cross-sectional view of an example of a conemirror with square base opening and an oval top opening.

FIG. 6E illustrates an example of a polygonal cross-section mirrors withreflective inside surfaces.

FIG. 7A illustrates a schematic side view of an example transparentcone-shaped collimation lens with a flat base.

FIG. 7B illustrates a schematic side view of an example transparentcone-shaped collimation lens with a concave semi-spherical base.

FIG. 7C illustrates an example of a directional light source includingthe transparent cone-shaped collimation lens.

FIG. 8A illustrates an example of a directional light source includingcommodity emitter.

FIG. 8B illustrates the commodity emitter in the directional lightsource.

FIG. 8C illustrates an optical flux distribution of the directionallight source with a distance of the light emitter and the lens equal to34 mm.

FIG. 8D illustrates an optical flux distribution of the directionallight source with a distance of the light emitter and the lens equal to36 mm.

FIG. 9A illustrates an example of a directional light source includingan emitter having a square flat emission surface, and a cone mirror witha square base opening and a circular top opening.

FIG. 9B illustrates an optical flux distribution of the directionallight source.

FIG. 10A illustrates an example of a directional light source includingan emitter having a round flat emission surface.

FIG. 10B illustrates an optical flux distribution of the directionallight source.

FIG. 11A illustrates an example of a directional light source includingan emitter having a square flat emission surface.

FIG. 11B illustrates the square LED emitter in the directional lightsource.

FIG. 11C illustrates an optical flux distribution of the directionallight source.

FIG. 12A illustrates an example of a directional light source includinga transparent collimation lens.

FIG. 12B illustrates an optical flux distribution of the directionallight source.

FIG. 13 illustrates an example of a light emitter and a cone mirror.

DETAILED DESCRIPTION

For a better understanding of the present invention, together with otherand further objects, advantages and capabilities thereof, reference ismade to the following disclosure and appended claims taken inconjunction with the above-described drawings.

At least one embodiment discloses an optics structure and relatedoptical devices to achieve a directional light source with a smalloptical beam divergence angle. Such light source can also be calledcollimated light source or quasi-collimated light source. The schematicdrawing of the basic structure for such directional light source isshown in FIG. 1. The light source (also referred to as light engine)includes a light emitter 1100 with small emission area, a cone-shapedmirror (also referred to as cone mirror) 1200 with a base opening 1220at the bottom. The cone mirror 1200 has a half-cone angle of about 30degrees. In some embodiments, the half-cone angle is larger than 30degrees. The light source further includes a focusing optical device1300. The light emitter 1100 may or may not be mounted on or placed onthe supportive base 1400. The light emitter 1100 is placed at the baseopening 1220 of the cone mirror 1200. FIG. 1 shows one embodiment of thecone mirror, which has a cone shape with a very small base opening 1220.Its center axis, as shown in FIG. 1, is a line that passes through thecenter of the base opening 1220 and the top opening 1210. It has acircular shape for its horizontal cross-sections, which are thecross-sections in the planes with the normal directional parallel to thecenter axis. The cone mirror 1200 has reflective sidewall surface(s)1250 that face inside. The reflective sidewall surface has a constantsidewall profile slope, which means that the intersection of this conemirror sidewall with any vertical plane in which the center axis lies inthat plane has a sidewall profile with constant profile slope. Thesidewall profile slope can be the same or different for each verticalplane that passes through the mirror's central axis as long as the slopehas a constant value for each cross-section. The height of the conemirror 1200, denoted as h, is much larger than the diameter of the basehole 1220, denoted as a. The light emitted from the light emitter 1100will enter the cone mirror through the hole at the base 1220. Theemission surface (also referred to as light output surface) of the lightemitter 1100 is located in close proximity to the base opening 1220 ofthe cone mirror 1200, so that all or most of the light emission fromemitter 1100 can enter the cone mirror, or be treated as entering thecone mirror, from the base opening 1220. Also, the dimension of theemission surface of the light emitter 1100 should be the same or closeto the dimension of the cone mirror base opening, such as dimensiondifference is less than 30% of the cone mirror base opening dimension,so that the emission surface of the light emitter 1100 and its image(s)formed by the cone mirror together can form a virtual-point light sourcewith directional light emission. A focusing optical device 1300, such asa collimation lens or curved surface, is placed in front of the topopening 1210 of the cone mirror 1200 to collect and collimate (alsoreferred to as concentrate) all of the light output from the cone mirroropening 1210 into an optical beam with small beam angle. The focusingoptical device 1300 may be in contact with or has some distance from thecone mirror 1200.

FIG. 2A shows a 3D drawing of a cone mirror 2200 with a light emitter2100 at or beneath the cone mirror base opening. Such structure resultsin a virtual-point source with directional light emission. To clearlyillustrate the reflective sidewall surface 2250 of the cone mirror 2200and the location of the emitter 2100, FIG. 2A shows half of the conemirror 2200 that cut half along a vertical plane 2280 passing throughthe center axis of the cone mirror 2200. The light emitter 2100 may ormay not be mounted or placed on the supportive base 2400. The outsidesurface 2290 of the cone mirror can have any profile.

The schematic drawings of cone mirror 2200 with light emitter 1100 atthe base opening is shown in FIG. 2B. The working principle of lightengine can be analyzed using image optics. Assume that the diameter ofthe emission surface of the emitter 2100 is slightly smaller than thediameter of the base opening of the cone mirror 2200. Light emitter 2100emits light in different directions. In FIG. 2B, the light beams 2501emitted from the light emitter 2100, whose original tilting angle offcone mirror axis is smaller than half cone angle, will directly exit thecone mirror's opening 2210 without any reflection from the cone mirror.

The light beams 2502, 2503, 2504 emitted from the light emitter 2100,whose original tilting angles off the cone mirror axis are larger thanhalf cone angle, will be reflected by the cone mirror and change itstilting angle into a value no larger than half cone angle. Because thecone mirror has a half cone angle of about 30° or larger, the lightbeams 2502, 2503, 2504 are reflected only once by the cone mirror,before the light beams change their tilting angles to values no largerthan half cone angle and exit from the cone mirror opening 2210. As aresult, no matter what the light emission pattern of the light emitter2100 has, all of the light beams emitted from emitter 2100 will beconfined by the cone mirror 2200 and exit the opening 2210 of the conemirror with minimized loss.

Using imaging optics, the light beams that are reflected by the conemirror can be treated as light beams emitted from the reflectionimage(s) of the light emitter 2100 caused by the cone mirror 2200. FIG.2C shows such reflection image(s). Light beams 2501, 2502, 2503, 2504are originally emitted from the light emitter 2100. Beam 2501 exits thecone mirror opening 2210 without any reflection. Beam 2502, 2503, 2504are reflected once (also referred to as first reflection) by the conemirror and become the light beams 2512, 2513, 2514, respectively. Lightbeams 2512, 2513, 2514 can be treated as light beams directly emittedfrom of the light emitter's image 2191. 2192 formed by the cone mirror,due to the fact that the cone mirror has a straight sidewall profile. Insome embodiment, the cone mirror, for example a polyhedral cone, canhave a plurality of reflective sidewalls, which can induce a pluralityof reflection images. Light beams 2592, 2593, 2594 are the images oflight beams 2502, 2503, 2504, respectively, in the cone mirror, as shownin FIG. 2C.

Overall, the light beams that exit the opening of the cone mirror 2210can be treated as the light beams that are emitted directly from thelight emitter 2100 and its reflection image(s) 2191, 2192 in cone mirror2200. If the diameter of the cone mirror base opening, denoted as a, issubstantially close to the effective dimension of light emitter 2100,the light emitter 2100 and its image(s) 2191, 2192 formed by the conemirror are very close to each other. Therefore, the emitter and imagestogether can be treated as a virtual point-source.

Above disclosures in FIG. 2B and FIG. 2C shows that all of the lightbeams exiting the cone opening 2210 can be treated as the light beamsdirectly emitted from the point-like source, which consists of lightemitter itself 2100, and its image(s) 2191, 2192 formed by the conemirror. This point-like source has a dimension of H, which may be largerthan a. Additionally, all of the light beams emitted from the lightemitter 2100 itself and its image(s) 2191, 2192 formed by the conemirror are confined within a beam angle, which is determined by the conemirror's cone angle. Therefore, the virtual point-source is adirectional virtual-point light source.

In the case that the effective dimension of the light emitter 2100 issubstantially the same as the cone mirror base hole, the light emitteritself 2100 and its image(s) 2191, 2192 formed by the cone mirror canform a virtual point-source having a emission area without any gap inbetween. All of the light emitted from light emitter 2100 will eitherdirectly exit the cone mirror opening 2210 or be reflected only once bythe cone mirror and exit the opening of the cone mirror 2210. Therefore,one of the advantages of such directional virtual-point light sourcetechnology is that the optical loss caused by the cone mirror isminimized. The only optical loss is caused by the one-time mirrorreflection. As a result, the total light output from the cone mirror2200 will be close to the total light emission from the emitter 2100.

The beam angle of the directional virtual-point light source shown inFIG. 2B and FIG. 2C is determined by the dimensions of the cone mirror,as shown in FIG. 2D. The beam angle, θ_(beam), is determined by theemitted beams 2571, 2572, which are not reflected by the cone mirror andhave the largest tilting angle. Therefore, the beam angle, θ_(beam), islarger than the cone angle, θ_(cone). The cone mirror's height, h, ismuch larger than the diameter of the cone mirror base opening, a. As aresult, the beam angle is very close to cone angle; θ_(beam)≈θ_(cone).The geometrical relationship in FIG. 2D shows that the beam angle,θ_(beam), can be calculated by,

θ_(beam)=2×tan⁻¹[(h×tan (θ_(cone)/2)×a)/h].  (1)

For example, if cone angle of the cone mirror is, ∂_(cone)=60°, and theratio between cone mirror height, h, and the cone mirror base openingdiameter, a, is h/a=10, the beam angle will be θ_(beam)=68.2°, which isvery close to the cone angle, θ_(cone)=60°.

For example, if cone angle of the cone minor, θ_(cone)=60°, and theratio between cone mirror height, h, and the cone mirror base diameter,a, is h/a=5, the beam angle will be θ_(beam)=75.7°, which is still not abig difference (25% larger) from cone angle, θ_(cone)=60°. In summary,the beam angle, θ_(beam), of the directional virtual-point light sourceis determined by the dimensions of the cone mirror. The higher the ratiobetween h and a is, the closer the beam angle, θ_(beam), and cone angle,θ_(cone) are. With a cone mirror 2200 with high ratio between h and a,the cone mirror 2200 can form a beam angle of the light emission fromthe emitter 2100 to a value close to the cone angle.

In one embodiment, a focusing optical device 3300 with proper focallength, for example focusing lens, can be placed on top of the conemirror top opening 3210, as shown in FIG. 3A , to achieve a directionallight source with small beam angle. The focusing optical device 3300 canbe in contact with the cone mirror 3200, or be placed at a certaindistance from the cone mirror 3200, or be placed inside the cone mirroropening 3210. The focusing optical device 3300 is big enough to collectsubstantially all of the light output from the cone mirror top opening3210. For example, if the focusing optical device 3300 is placed on andin contact with the top of the cone mirror opening 3210, the diameter ofthe focusing optical device 3300 can be the same as or larger than thediameter of cone mirror opening 3210, b. If the focusing optical device3300 is placed inside cone mirror opening 3210, the focusing opticaldevice 3300 can be placed with its edge in contact with the cone mirrorsidewall. If the focusing optical device 3300 is placed on top of conemirror opening 3210 with some distance from the cone mirror, thediameter of the focusing optical device 3300 is larger than the diameterof the cone mirror opening 3310, b. The diameter is extended to a valuethat is large enough to collect all of the light output from the conemirror opening 3210. As a result, the distance between the focusingoptical device and the virtual point-source, s, can be equal to, largerthan, or smaller than the height of the cone mirror, h.

The focusing optical device 3300 can be any optical device with anoptical focusing function. The options of the focusing optical deviceare, but not limited to, spherical lens, aspheric lens, Fresnel lens,curved surface, or others. To achieve a collimated beam or optical beamwith very small beam angle, the focal length of the focusing opticaldevice 3300 should be similar or close to the distance, s, between thefocusing optical device 3300 and the virtual-point light sourceconsisting of light emitter 3100 and its image(s) 3191, 3192. In otherwords, the focal point of the focusing optical device is in closeproximity of the virtual-point light source. All of the light beams canbe treated as light emitted from the point-like source, which includeslight emitter 3100 and its images 3191, 3192 formed by cone mirror.Therefore, the focusing optical device 3300 can convert all of the lightbeams into a collimated beam, i.e. an optical beam with small beamangle, as shown in FIG. 3A.

The beam angle of the optical beam output from the optical focusingdevice 3300 is determined by the size of the virtual point-source, H,which consists of light emitter 3100 together with its images 3191, 3192formed by the cone mirror 3200, and the distance, s, between thefocusing device 3300 and the point-like source consisting of lightemitter 3100 itself and its image(s) 3191, 3192,and the focal length ofthe focusing optical device 3300. To have a small beam angle for thelight output from the light source, the effective focal length of thefocusing optical device 3300 has a value close to the distance, s, sothat the focusing optical device 3300 can collimate or concentrate thelight emitted from the virtual-point source, which consists of the lightemitter 3100 and the its image(s) 3191, 3192, to a beam with very smallbeam angle. Additionally, the larger the ratio between distance, s, overdimension, H, is, the smaller possible beam angle can be achieved forthe optical light output from this directional light source.

The beam angle of the light output from the directional light source,and its relationship with the dimension of the light emitter 3100 andthe cone mirror 3200, and the location of focusing optical device 3300can be analyzed as shown in FIG. 3B. The dimensions used in FIG. 3B comefrom the dimension of the light source shown in FIG. 3A. The cone mirrorhas a base opening with a diameter of a. The effective diameter of thelight emitter 3100 is equal to or smaller than the base diameter, a. Thediameter of the virtual-point light source 3150, which includes lightemitter 3100 and its image(s) 3191, 3192 formed by cone mirror 3200, isH, which is about two time of a if the cone angle is θ_(cone)=60° forthe cone mirror. The effective distance from the virtual point-source3150 to the optical focusing device 3300, is s. The optical focusingdevice 3300 works as a projection lens which can project an image of thevirtual-point source 3150 with dimension of H, to a plane with adistance of s′. An illuminated spot 3180 with dimension of H′ is formed;and hence a directional light beam can be formed. As the projected image3180 with dimension of H′ is focused at a plane that is substantiallyfar away from the light source, or even at infinity distance, the beamangle, θ, of the light output beam from the light source is the smallestpossible beam angle, and can be determined by the dimension of thislight source, and can be calculated by following,

θ=2×tan⁻¹ [H′/(2s′))]=2×tan⁻¹ [H/(2s)]  (2)

Therefore, the smallest beam angle of the light beam output from thelight source in the embodiment, is determined by the dimension of thelight emitter and the cone mirror. To have a small beam angle, and hencemore concentrated light power, the dimension ratio H/s should be small.That means that the cone mirror base diameter is much smaller thandistance between the focusing optical device 3300 and the virtual-pointsource 3150. For example, if the H/s=0.1, a beam angle of about 11.4°can be achieved; if H/s=0.079, a beam angle of about 9.0° can beachieved.

In some embodiments, the focal length of the focusing optical device3300 is not necessary to match the distance, s. Focusing optical device3300 with a variety of focal lengths can be used. As a result, a lightsource with different beam angles can be achieved. In some embodiments,even optical device(s) with negative focal length(s), such as adiverging lens, can be used to achieve a light source with a very largebeam angle.

In one embodiment, the focal length of the focusing optical device 3300,and its distance, s, from the virtual point source 3150 can be properlychosen so that the projected image 3180 of the virtual point source 3150has a reasonable uniformity. Virtual point-source 3150 includes lightemitter 3100, and its image(s) 3191, 3192 formed by the cone mirror3200, as shown in FIG. 3A. There may be gaps between light emitteritself 3100, and its image(s) 3191, 3192. Therefore, there is apossibility that the projected image 3180 of virtual-point source 3150can have such gaps on the illuminated plane although this gap is verysmall, if the focusing optical device 3300 is placed at a certaindistance, s, so that it can well focus the image of gap features fromthe virtual point source onto the illuminated area. To achieve a uniformillumination from this directional light source, the focusing opticaldevice 3300 should be placed at a certain distance, s, that theilluminated area should have reasonable uniformity with smoothtransition between light emitter's projected image and the projectedimage of light emitter's image(s) in cone mirror. The dimension of thelight emitter and the diameter of the light emitter can be substantiallyclose to each other so that the light output from the directional lightsource, which includes light emitter, cone mirror and focusing opticaldevice, enables an illumination pattern with good uniformity.

FIG. 4A shows a drawing of the cone mirror 4200. To clearly illustratethe reflective surface 4250 of the cone mirror 4200, FIG. 4A shows thecone mirror 4200, cut half along a vertical plane 4280 that goes throughthe center axis of the cone. The cone-shaped mirror 4200 has areflective sidewall surface 4250, which has a constant sidewall profileslope at the intersection of the cone mirror sidewall surface with anyplane in which the center axis lies in, with a slope angle,θ_(half-cone), or also called half-cone angle, about 30° or larger. Anysuitable materials can form the reflective surface. For example, thecone mirror can be fabricated by coating a reflective layer on theinside surface 4250 of the cone. The cone mirror can also be fabricatedby polishing a metal cone to achieve the specular reflection on thesurface 4250. The cone mirror can further be achieved using totalinternal reflection by forming a cone on the light emitter usinghigh-index optical material, so that the total internal reflection willhappen at the cone surface. The cone mirror can be fabricated using anyother means as long as it provides a reflective cone surface 4250.

The cone angle of the cone mirror is double of the θ_(half-cone).Accordingly, the cone angle of the cone mirror is about 60° or larger.The curvature or shape of the outside surface 4290 of this cone mirror4200 can be anything, as long as it does not affect its insidereflective surface 4250. The cone mirror 4200 has a base opening 4220with a diameter, a. The height of the cone mirror 4200 is h, which ismuch larger than the base opening 4220 diameter, a. The cone mirror hasa top opening with diameter of b, which is much larger than the baseopening 4220 diameter, a, based on the geometrical relationship.

The base opening of the cone mirror is where light enters the conemirror. The edge 4225 of the base opening 4220, as shown in FIG. 4B, cutin half along a vertical plane 4280 that goes through the center axis ofthe cone., can be sharp so that the light can only be reflected by thecone surface with slope angle of θ_(half-cone), as soon as it enters thecone mirror base opening 4220. In some embodiments, wherein the emitteris located inside the cone mirror, this sharp edge may not be required.The bottom 4221 of the cone mirror is not necessary to be horizontallyflat. It may be conformal to the emitter's supportive base 1400 as shownin FIG. 1 to provide mechanical support to the cone mirror. It can alsohave other curvatures as long as it enables the cone mirror to confinethe emitter 4100 inside or beneath the base opening 4220.

To maximize the light emitted from the emitter 5100 entering the conemirror, the emitter is located inside the cone mirror base or justbeneath the cone mirror base. Also, the diameter of the cone mirror baseopening, a, should be equal to or smaller than, but preferably close tothe dimension of the emission surface of the emitter 5100 which isdefined by the physical boundary of the emitter's emission surface. Forexample, FIG. 5A shows a side view of a flat emitter 5100. Only aportion of the cone mirror 5200 is shown in FIG. 5A. The emission area5101 is embedded inside other components 5150, such as the mechanicalframe, of the emitter 5100. The emission area 5101 may be or may not becovered by a protection optical window on the top. The whole emitter5100 is placed beneath the cone mirror 5200 with the cone mirror baseopening 5220 located above the emission area 5101. The cone mirrorbottom is conformal to the emitter frame 5150 such that all of or themajority of the light emission from the emission surface can enter thecone mirror. The sharp edge 5225 of the cone mirror may ensure that thelight emission emitted to the side can be reflected only by the conemirror surface with slope angle of θ_(half-cone).

In FIG. 5A, the emission surface 5101 of the emitter 5100 has thediameter equal to the diameter of cone mirror base opening 5220, a. Theedge of the cone mirror base opening 5220 is well aligned with thephysical boundary of the emission surface 5101. Only a portion of thecone mirror 5200 is shown in FIG. 5A. In some embodiments, the emissionsurface 5101 of emitter 5100 can be larger than area of cone mirror baseopening 5220. In such case, the emission area that are directly beneaththe cone mirror base opening 5200 will primarily contribute to the lightemission that enter the cone mirror. In some other embodiments, theemission area 5101 of the emitter 5100 can be smaller than the area ofcone mirror base opening 5220. In such cases, the emission area 5101 ofthe emitter 5100 and the area of cone mirror base opening 5220 aresubstantially close, such as their diameter difference is less than 30%of the base opening diameter, so that the emission surface 5101 and itsimage(s) formed by cone mirror together can form a virtual point lightsource.

FIG. 5B illustrates an embodiment of light emitter 5100. Only a portionof the cone mirror 5200 is shown in FIG. 5B. The light emitter 5100includes light emitting device 5110, reflective cup 5120, optical window5101, and frame 5150. In such a light emitter 5100 structure, theoptical window 5101 can be treated as the emission surface of thisemitter, because all of the light emission from the emitting device5110, is collected by the reflective cup 5120 and output from theoptical window 5101. Therefore, the cone mirror is placed above theemitter 5100 with cone mirror base opening 5220 well aligned withoptical window 5101. The cone mirror bottom is conformal to the emitterframe 5150 so that all of or the majority of the light emission from theoptical window 5101 can enter the cone mirror. The sharp edge 5225 ofthe cone mirror can help to confine the side emission such that light isonly reflected by the cone mirror surface with a slope angle ofθ_(half-cone).

In FIG. 5B, the optical window 5101 of the emitter 5100 has the diameterequal to the diameter of cone mirror base opening 5220, a. The edge ofthe cone mirror base opening 5220 is well aligned with the physicalboundary of the optical window 5101. In some embodiments, the opticalwindow 5101 of emitter 5100 can be larger than area of cone mirror baseopening 5220. In such a case, the optical window area that is directlybeneath the cone mirror base opening 5200 primarily contributes to thelight emission that can enter the cone mirror. In some embodiments, theoptical window 5101 of the emitter 5100 can be smaller than the area ofcone mirror base opening 5220. In such cases, the area of the opticalwindow 5101 of the emitter 5100 and the area of cone mirror base opening5220 should be substantially close, such as their diameter difference isless than 30% of the base opening diameter, so that the optical window5101, as the emission surface, and its image(s) in cone mirror togethercan form a virtual point-source.

FIG. 5C shows another embodiment of emitter 5100 beneath cone mirrorbase opening 5220. Only a portion of the cone mirror 5200 is shown inFIG. 5C. The emitter 5100 includes light emitting device 5110,transparent dome lens 5101, and frame 5150. All of the light emittedfrom the emitting device 5110, exits the emitter 3100 through the domelens 5101. Thus, the transparent dome lens 5101 can be treated as theemission surface of this emitter. To maximize the light emissionentering the cone mirror, the emitter 5100 is placed in a way that thewhole dome lens 5101 is inside the cone mirror base opening as shown inFIG. 5C. The cone mirror bottom is conformal to the emitter frame 5150so that all of or the majority of the light emission from the dome lens5101 can enter the cone mirror. The sharp edge 5225 of the cone mirrormay help to confine side light emission such that light is onlyreflected by the cone mirror surface with slope angle of θ_(half-cone).In FIG. 5C, the dome lens 5101 of the emitter 5100 has a horizontaldimension equal to or smaller than the diameter, a, of cone mirror baseopening, because it is completely inside the cone mirror opening. Thedome lens 5101 area of the emitter 5100 and the area of cone mirror baseopening are substantially close, such as their diameter difference isless than 30% of the base opening diameter, so that the dome lens 5101,as the emission surface, and its image(s) formed by the cone mirrortogether can form a virtual-point light source.

FIG. 5D shows another embodiment of emitter 5100. Only a portion of thecone mirror 5200 is shown in FIG. 5D. The emitter 5100 includes lighttransmission device 5105, with a light exit surface 5101 at the top. Thelight transmission device can be any optical device that can confine andtransmit the light inside and output the light at the end surface. Theycan be, but not limited to, optical fiber, fiber bundle, light guide,waveguide, and others. The light output from the light exit surface 5101of the light transmission device 5105 enters the cone mirror. Tomaximize the light emission entering the cone mirror, the lighttransmission device 5105 should be placed in a way that its light exitsurface 5101 should be at the base of the cone mirror or inside the conemirror base opening.

As shown in FIG. 5D, the distance between light exit surface and conemirror base is denoted as d. Distance d, is small, for example d<a, sothat all of the light emitted from light exit surface 5101 can betreated as light coming from the base opening of the cone mirror. Insome embodiments, the cone mirror bottom is not necessary to behorizontally flat. It can have a vertical wall to help to confine thelight transmission device inside the cone mirror base opening. The edge5225 of the cone mirror base opening can be sharp to help confine sidelight emission such that light is only reflected by the cone mirrorsurface with a slope angle of θ_(half-cone).

In FIG. 5D, the diameter of the light exit surface 5101 is equal to orsmaller than the diameter, a, of cone mirror base hole, because it iscompletely inside the cone mirror hole. The light exit surface 5101 areaof the light transmission device 5100 and the area of cone mirror baseopening 5220 are substantially close, such as their diameter differenceis less than 30% of the base opening diameter, so that the light exitsurface 5101, as the emission surface, and its image(s) formed by conemirror together can form a virtual point-source. The light exit surface5101 area of the light transmission device 5100 can be larger than thearea of the cone mirror base opening 5220, if the light exit surface5101 is beneath the cone mirror base opening 5220. In such case, area oflight exit surface 5101 directly beneath of the cone mirror base opening5220 primarily contributes to the light emission that can enter the conemirror.

In some embodiments, there are other possible configurations to arrangethe light emitter and cone mirror. The light emitter and the cone mirrorare arranged in a way that the emission from the light emitter to enterthe cone mirror from its base opening with minimized optical loss.Further, the cone mirror base opening is small enough such that the gapbetween the cone mirror base opening and the light emitter is minimized.

FIG. 5E shows a top view of an embodiment of an emitter 5100 located atthe base of the cone mirror 5200. In this embodiment, the emitter 5100has a circular emission area 5101. The emission area can be the directemission area as in FIG. 5A, or the optical window as in FIG. 5B, or thedome lens surface as in FIG. 5C, or the light exit surface as in FIG.5D, or emission surface of other emitters. The diameter of the emissionarea 5101 should be equal to or slightly smaller, such as less than 30%,than the diameter of cone mirror base opening, a, such that the emissionarea 5101 and its image(s) formed by the cone mirror together can form avirtual point-source. In some embodiments, the diameter of the emissionarea 5101 can be larger than the diameter, a, of the cone mirror baseopening while still enable the formation of virtual point-source. Thelight emitted from the emission surface within the edge 5225 of the conemirror base opening enters the cone mirror.

FIG. 5F shows a top view of another emitter located at the base of thecone mirror 5200. In this case, the emitter has a square emission area5101. The emission area can be the direct emission area as in FIG. 5A,or the optical window as in FIG. 5B, or the dome lens surface as in FIG.5C, or the light exit surface as in FIG. 5D, or the emission surface ofother light emitters. The largest dimension of this square emissionsurface 5101 is the length of its diagonal line. To ensure all of thelight emission from the emission surface can enter the cone mirror, thediameter, a, of cone mirror base opening, is equal to or larger than thelength of the diagonal line of the square emission surface, as shown inFIG. 5F. Additionally, the emission area 5101 should be large enough,such as its diagonal should be close to, or lightly smaller, such asless than 30%, than the diameter of cone mirror base hole, a. so thatthe emission area 101 and its image(s) formed by the cone mirrortogether can form a virtual point-source.

In some embodiments, the diagonal of the emission area 5101 is largerthan the diameter, a, of the cone mirror base opening. This can stillenable the formation of virtual point-source. The light emitted from theemission surface within the edge 5225 of the cone mirror base openingcan enter the cone mirror. In other embodiments, the emission surface ofthe emitter can be in other shapes. The cone mirror base opening canalso be in shapes other than circle. The dimension of the cone mirrorbase opening is large enough such that all or most of the light emittedfrom the emitter can enter the cone mirror through the base opening.Meanwhile, the dimension of the cone mirror base opening should also besmall enough so that it can be close to the dimension of the emissionsurface of the emitter so that a virtual point-source can be formed,which includes emission surface of the emitter, and its image(s) formedby the cone mirror. For example, the smallest gap between the edge ofthe cone mirror base opening and the emitter's emission surface boundarycan be less than 30% of the dimension of the cone mirror base opening.

In one embodiment, the cone mirror is used to collect the light emissionwith broad angular distribution to form a directional virtual-pointsource. Such a mirror does not necessarily have a circularcross-sectional shape, as described in previous figures. Squarecross-section mirrors or polygonal shape cross-section mirrors withreflective sidewall surfaces, as shown in FIGS. 6A-6E, with a baseopening can also be used to collect the light emission with broadangular distribution from the light emitter to form a directionalvirtual-point source and be used as a component for the directionallight source fabrication.

FIG. 6A shows a square cross-sectional mirror with reflective sidewallsurfaces. To clearly illustrate the reflective surfaces of the mirror,only half of this mirror is drawn. The vertical central plane 6280 ofthe mirror goes through the central axis of the mirror. The slope angleof the reflective surface 6250 is about, θ_(half-cone)=30° or larger.The outside surface 6290 of the mirror can have any curvature. Theheight, h, of the mirror is much larger than the dimension of the baseopening, a. A square light emitter, such as, but not limited to, LEDemitter, can be placed at the base or beneath the base opening 6220 toenable a virtual-point source with light emission toward to a solidangle that is defined by the square cross-sectional mirror.

A top view of the square emission surface 6101 of the light emitterplaced at the base of the square cross-sectional mirror is shown in FIG.6B. The emitter can also be placed in other orientations. The dimensionsof the square emission surface 6101 of the light emitter issubstantially close to, such as less than 30%, the dimensions of themirror base opening so that the emitter's emission surface 6101 and itsimage(s) formed the reflective surfaces of the mirror can be close toeach other to form a virtual point-source. In some other embodiments,light emitter having emission surface with other shapes, such as, butnot limited to, rectangles, circles, ovals and others, can also be usedwith this square cross-sectional mirror, as long as their dimensions issubstantially close to the dimension of the base opening dimension, suchas that the smallest gap between emission surface of the emitter and themirror base opening edge is less than 30% of the dimension of mirrorbase opening, to enable a virtual point-source. Similarly, in anotherembodiment, a rectangular cross-sectional mirror with a rectangular basehole and mirror top opening can also be used. A rectangular-shaped lightemitter or other shape emitter can be placed at the base to enable avirtual point-source.

In one embodiment, the mirror has different shapes at the base opening6220 and top opening 6210 as shown in FIG. 6C. To clearly illustrate thereflective surface(s) of the mirror, only half of this mirror is drawn.The vertical central plane 6280 of the mirror goes through the centralaxis of the mirror. The base opening 6220 of the mirror has a squareshape. The top opening 6210 of the device has a circular shape. Theshape of the base opening 6220 and top opening 6210 of the mirror can beany other shape, such as, but not limited to a, rectangle, triangle,oval, polygon, or others. The reflective surface 6250 of the mirror hasa constant profile slope at the intersection of the mirror's reflectivesurface with any plane in which the center axis lies in, with a slopeangle about, θ_(half-cone)=30° or larger. The outside surface 6290 ofthe mirror can have any curvature. The height, h, of the mirror is muchlarger than the dimension of the base opening, a. A square lightemitter, such as, but not limited to, LED emitter, can be placed at thebase or beneath the base hole to enable a virtual-point source withlight emission toward to a solid angle that defined by the mirrordevice. The light emitter with square emission surface 6101 can beplaced in the base opening 6220 as shown in FIG. 6B, or otherorientation. Light emitter with emission surface having other shapes,such as, but not limited to, rectangle, oval, circle, triangle, polygon,irregular shape, or others, can also be used.

In one embodiment, the mirror device has different shapes at the baseopening and at top opening as shown in FIG. 6D. To clearly illustratethe reflective surface of the mirror, only half of this mirror is drawn.The vertical central plane 6280 of the mirror goes through the centralaxis of the mirror. The base opening 6220 of the device has a squareshape. The top opening 6250 of the device has an oval shape. As aresult, the slope angles of the reflective surface 6250 at differentorientations, θ_(half-cone) and θ′_(half-cone) have different values.The shape of the base opening and top opening of the mirror can be anyother shape, including symmetric and asymmetric shapes. The reflectivesurface of the mirror always has a constant profile slope at theintersection with any plane in which the center axis lies in, althoughthis profile slope may have different angle value at each intersectionplane. Additionally, any slope angle, θ_(half-cone) or θ′_(half-cone),of the inside reflective surface 6250 is about 30° or larger. Theoutside surface 6290 of the mirror can have any curvature. The height,h, of the mirror is much larger than the dimension of the base opening,a. A light emitter with shape same as or different from the mirror baseopening 6220 can be placed at the base or beneath the base opening toenable a virtual point-source with light emission toward to a solidangle that defined by the mirror device.

Other polygonal cross-section mirrors with reflective surfaces, such asshown in FIG. 6E can also be used. Also, in some embodiments, polygonalcross-section mirror with cross-section having different shapes, suchas, but not limited to a square at the base and circle at the top, or arectangle at the base and square at the top, or a circle at the base andpolygonal at the top, or other combination of geometries, can be used,as long as the sidewall profile has a constant slope at the intersectionwith any plane in which the center axis lies in The sidewall profileslope can be the same or different at different intersection planes aslong as the slope has a constant value for each intersection plane.

In one embodiment, the cone mirror and optical focusing device togetherforms the collimation optics for the light emitter, which can collimatethe light emission from a light emitter with minimized optical loss. Inthis collimation optics, the cone mirror has a small opening at thebase, which has a diameter much smaller than the height of the conemirror. The slope angle of the reflective sidewall of the cone mirror isabout θ_(half-cone)=30° or larger. The optical focusing device islocated at the top of the cone mirror with a focal point located at theproximity of the cone mirror base opening. The optical focusing deviceshould be in contact with or proximal to the cone mirror top opening andits edge, such that minimal light can escape from this collimationoptics.

Such a collimation optics can also been realized by a transparentcone-shaped collimation lens using total internal reflection at the sideand curved focusing interface at the top, as shown in FIG. 7A. Aschematic side view of this transparent cone-shaped collimation lens isshown in FIG. 7A. In one embodiment, this collimation lens is made oftransparent material, such as glass, plastics, epoxy, silicone,encapsulant or any other transparent optical material. It can bemachined, molded or fabricated using other means to achieve itsgeometry. It has a small base 7220, which is the receiving end toreceive the light emission from the light emitter. Its sidewall surface7250 has a constant profile slope at the intersection with any plane inwhich the center axis lies, with slope angle of about θ_(half-cone)=30°or larger. The surface of the sidewall 7250 is smooth so that totalinternal reflection can occur for the light inside the lens that hitsthe sidewall 7250. In other embodiments, this total internal reflectionsurface 7250 can be fully or partially coated with a reflective coating,such as a metal layer, dielectric layers, and other coatings, to achievethe surface reflection without affecting the collimation function ofthis cone-shape collimation lens.

The total internal reflection sidewall can be considered as a conemirror 7200. The top surface of this collimation lens has a curvaturesuch that the curved interface 7300 between lens material and ambient,such as air, can have a collimation or concentration function, and canbe treated as an optical focusing device. Therefore, the optics analysisdescribed in previous paragraphs can be applied on this collimationlens. The curvature of the top surface 7300 should be chosen to enable afocal point of this curved surface 7300 at the proximity of the base7220 of the lens to achieve a small output optical beam angle. Theheight, h, of cone-shaped sidewall of the lens is much larger thandiameter of base, a, such that the base, as the light receiving end, andits image(s) formed by the total internal reflection surface 7250 can bea virtual-point light source with respect to the curved top surface7300, as an optical focusing device 7300. The curvature of the topsurface can be any one as long as its focal point is in the proximity ofthe base 7220. For example, aspheric curvature, spherical curvature,Fresnel surface, and others, all can be used for top surface 7300. Thecollimated or concentrated beam angle for light output from thiscollimation lens can vary depending on the curvature of the top surface.For example, an aspheric top surface may enable a beam with a smallerbeam angle compared to a spherical top surface. The curvature of the topsurface 7300 can also be chosen to have a variety of focal lengths suchthat its focal point can be close or far away from the base 7220 of thelens. As a result, the output optical beam with a variety of beam anglecan be achieved if such a lens is applied to the light emitter.

In some embodiments, the base 7220 of this cone-shaped collimation lensis not necessarily flat. Its surface morphology is designed to maximizethe collection of light emission from light emitter For example, if thelight emitter has a flat emission surface, the cone-shaped collimationlens base 7220 can have a flat surface, as shown in FIG. 7A, to conformto the emission surface of the emitter. If the light emitter 7100 has aspherical dome emission surface, such as in Cree's XLamp emitters, thecone-shaped collimation lens base 7220 can have a concave semi-sphericalshape, as shown in FIG. 7B, to conform to the emission surface of theemitter, so that the light collection by the cone-shaped collimationlens base 7220 can be maximized. To clearly illustrate the geometry ofthe collimation lens base 7220 with concave semi-spherical curvature, across-sectional view of the lens base that cut half along the planepassing through the center axis of the collimation lens is also shown inFIG. 7B. The concave semi-spherical curvature of the collimation lensbase 7220 shown in the FIG. 7B should have a diameter similar to thediameter of the light emitter dome lens that the collimation lens is tobe attached to, such that the collimation lens can conform to the domelens of the emitter. Since the base dimension, a, is much smaller thanthe height, h, and the diameter, b, the base 7220 morphology does notsignificantly affect the collimation function of the collimation lens.The collimation lens base 7220 can have any curvature or shape toconform to the emitter surface to maximize the light emission enteringthe collimation lens.

The cone-shaped collimation lens as shown in FIG. 7A and FIG. 7B, can beinstalled on top of the light emitter 7100 to enable a directional lightsource with a small beam angle, as shown in FIG. 7C. The cone-shapedcollimation lens base 7220 should be on the emission surface 7101 of theemitter 7100 so that light emission can enter the collimation lensthrough the base 7220. The cone-shaped collimation lens can bemechanically disposed on top of the emitter 7100, or attached on top ofthe emitter 7100 using an optical adhesive, such as epoxy, silicone,eucapsulant, polymers, and others. The cone-shaped collimation lens canalso be directly packaged together with the emitter 7100 to achieve anintegrated directional light source, such as shown in FIG. 7B. Forexample, the cone shaped collimation lens can be packaged with the LEDchip together to enable the directional light source using LEDs. Thedimension of the collimation lens base 7220 can be the same as, orlarger than but close to, the dimension of emission surface area suchthat all of the light emission from the emitter can be received by thecollimation lens to form a virtual-point source consisting of emissionsurface itself and its image(s) formed by the total internal reflectionsurface 7250. Light is eventually collimated or concentrated and thenoutputs from the top surface of the lens 7300. In some embodiments, thecurvature of the top surface 7300 of the cone-shaped collimation lenscan vary to achieve other focal lengths, so that its focal point is atsome distance away from the light emitter. As a result, different beamdivergence angles of the output optical beam can be achieved. Inaddition, the cross-section of the collimation lens can have shapesother than circular shapes, such as, but not limited to, squares,rectangles, other polygonal shapes, or others. Also, the collimationlens can have any of the geometries that a cone mirror can have asdiscussed in the previous embodiments.

FIG. 8A illustrates one embodiment of a directional light source. In theembodiment, the example light emitter 8100 used is a Cree's XLamp XM-Lemitter, which has a LED chip 8101 with area of about 2 mm×2 mm, asshown in FIG. 8B. The LED chip has a Lambertion emission pattern. TheLED chip is encapsulated inside a transparent silicone dome lens 8181which has diameter of about 4.4 mm. Therefore, the overall diameter ofthe emitter 8100 is 4.4 mm. The light emitter 8100 is placed beneath thebase of the cone mirror 8200 which has a circular base opening and acircular top opening, as shown in FIG. 8B. The diameter of the conemirror base is a=4.6 mm, which is very close to the diameter of theemitter 8100. The height of the cone mirror is h=34 mm. The opening ofthe cone mirror has a diameter of b=44 mm. The cone mirror has areflective surface, such as a silver coated surface, with a reflectivityof 98%. In other embodiments, the reflectivity of the cone mirror can beother values. A plano-convex aspheric lens 8300 is placed on top of thecone mirror, as shown in FIG. 8A. The lens has a diameter of 50 mm andan effective focal length of 50 mm. The surfaces of the lens are coatedwith anti-reflection coatings and have no surface reflections. In otherembodiments, the surface reflection of the lens can also be othervalues.

The following ray tracing simulations help to visualize the performanceof the directional light source disclosed in the previous paragraph. Thesimulated optical flux distribution at a surface that is 5 meters awayis shown in FIG. 8C. The distance between the light emitter 8100, andthe backside of the lens 8300 is l=34 mm. The simulation shows that at 5meters away from the light source, almost all the optical power that isoriginally emitted from the light emitter 8100 is concentrated into acircular area with a diameter of 100 cm. The simulation result alsoshows that the light beam output from the light source has a uniformoptical flux distribution. The beam angle of the concentrated lightoutput from the light source is about 10°.

If the focusing lens 8300 is placed some distance further away from thelight emitter 8100 such that the distance between its backside and thelight emitter 8100 is l=36 mm. The simulated optical flux distributionat a surface that is 5 meters away is no longer uniform, as shown inFIG. 8D. The simulation shows that almost all of the optical power thatoriginally emitted from the light emitter 8100 is concentrated into acircular area with diameter of 120 cm. However, the illuminated spot isno longer uniform. The center 8185 of the simulated illumination spotshown in FIG. 8D is the projected image of the LED chip from lightemitter. The surrounding area 8181 of the simulated illumination spotshown in FIG. 8D is the projected image of emitter's cone mirror image.The only difference between these two simulations is the distance, l, offocusing lens 8300. The ray tracing simulations clearly show that thefocusing optical device has to be properly placed so that the uniformillumination can be achieved by the directional light source.

Another embodiment of a directional light source with concentrated lightoutput is shown in FIG. 9A. The light emitter 9100 used in thissimulation is a LED emitter with a flat emission surface 9101. Theemission surface 9101 is square of 3 mm×3 mm. The LED chip has aLambertion emission pattern. The cone mirror has a square base openingof 3 mm×3 mm.The light emitter 9100 is placed beneath the base of thecone mirror 9200 which has a square base opening and circular topopening 9210. The LED emission surface 9101 is well aligned with conemirror base opening so that there is no gap between them. The height ofthe cone mirror is h=34 mm. The circular top opening of the cone mirrorhas a diameter of b=44 mm. The cone mirror has a reflective surface,such as a silver-coated surface, with a reflectivity of 98%. In someembodiments, the reflectivity of the cone mirror can be other values. Aplano-convex aspheric lens is used as the focusing optical device 9300,and is placed on top of the cone mirror, as shown in FIG. 9A. The lenshas a diameter of 50 mm and an effective focal length of 50 mm. Thedistance between the light emitter 9100, and the backside of the lens9300 is l=36 mm. The surfaces of the lens are coated withanti-reflection coating(s) and have no surface reflections. In someembodiments, the surface reflection of the lens can be other values.

Ray tracing simulation is also performed on the configurations ofdirectional light source illustrated in FIG. 9A. The simulated opticalflux distribution at a surface that is 5 meters away is shown in FIG.9B. The simulation shows that at 5 meters away from the light source,most of the optical power that originally emitted from the light emitter9100 is concentrated into a circular area with about a diameter of 60cm. In some embodiments, the focusing lens 9300 can be placed in otherpositions to achieve a different beam angle of the concentrated lightbeam from this light source.

Another embodiment of a directional light source with concentrated lightoutput is shown in FIG. 10A. The light emitter 10100 used in thisexample has a round flat emission surface with a diameter of 4.6 mm,which is the same as the diameter of the cone mirror base. The lightemitter 10100 has a Lambertion emission pattern. This light emitter10100 is located at the base of a concave cone mirror 10200, which hasbase diameter of a=4.6 mm. In some embodiments, the diameter of thelight emitter 10100 can exceed the diameter of the cone mirror base, a.Only light emission emitted by the emission surface directly beneath thecone mirror base opening can enter cone mirror and contribute to theoutput light of this directional light source. The height of the conemirror is h=34 mm. The opening of the cone mirror is b=44 mm. The conemirror has a reflective surface, such as a silver-coated surface, with areflectivity of 98%. In other embodiments, the reflectivity of the conemirror can be other values. A plano-convex aspheric lens 10300 is placedon top of the cone mirror, as shown in FIG. 10A. The lens has a diameterof 50 mm and an effective focal length of 50 mm. The distance betweenthe light emitter 10100, and the backside of the lens 10300 is l=34 mm.The surfaces of the lens are coated with anti-reflection coating(s) andhave no surface reflections. In some other embodiments, the surfacereflectivity of the focusing lens can be other values.

The simulated optical flux distribution at a surface that is 5 metersaway is shown in FIG. 10B. The simulation shows that at 5 meters awayfrom the light source, most of the optical power that originally emittedfrom the light emitter 10100 is concentrated into a circular area with adiameter of 100 cm. The simulation result also shows that the light beamoutput from the light source has a uniform optical flux distribution. Insome other embodiments, other focusing optical devices can be used. Inaddition, different focal lengths of the focusing optical device can bechosen to achieve different beam angles of concentrated light output.

Yet another embodiment of a directional light source with concentratedlight output is shown in FIG. 11A. The light emitter 11100 used in thisembodiment has a square flat emission surface 11101 with dimension of 3mm×3 mm, as shown in FIG. 11B. The light emitter 11100 has a Lambertionemission pattern. This light emitter 11100 is located inside the base ofa concave cone mirror 11200, which has base diameter of 1=4.6 mm. Theheight of the cone mirror is h=34 mm. The opening of the cone mirror isb=44 mm. The cone mirror has a reflective surface, such as a silvercoated surface, with reflectivity of 98%. In some embodiments, thereflectivity of the cone mirror can be other values. A plano-convexaspheric lens 11300 is placed on top of the cone mirror, as shown inFIG. 11A. The lens has a diameter of 50 mm and an effective focal lengthof 50 mm. The distance between the light emitter 11100, and the backsideof the lens 11300 is l=34 mm. The surfaces of the lens are coated withanti-reflection coating(s) and have no surface reflections. In someother embodiments, the surface reflectivity of the focusing lens can beother values.

The simulated optical flux distribution at a surface distance of 5meters is shown in FIG. 11C. The simulation shows that at 5 meters awayfrom the light source, most of optical power that originally emittedfrom the light emitter 11100 is concentrated into a circular area with adiameter of 100 cm. The simulation result also shows that the light beamoutput from the light source has a uniform optical flux distribution. Insome other embodiments, other focusing optical devices can be used. Inaddition, different focal lengths of the focusing optical devices can bechosen to achieve different light output beam angles.

Still another embodiment of a directional light source with concentratedlight output is shown in FIG. 12A. The light emitter 12100 used in thisembodiment has a circular flat emission surface with a diameter of 4.4mm. The light emitter 12100 has a Lambertion emission pattern. Atransparent collimation lens 12200 with cone shape, similar to thecollimation lens shown in FIG. 7A, is placed on top of the emitter12100. The sidewall 12250 of the cone-shaped lens can cause totalinternal reflection so that it can be treated as a reflective conemirror surface. The base diameter of this collimation lens is a=4.6 mm.The height of the cone is h=34 mm. The diameter of the top surface isb=44 mm. This collimation lens can be, but not limited to, made ofsilicone, epoxy, glass, plastics or any other transparent material. Inthis simulation, silicone is the material used to this cone-shapedcollimation lens. A spherical curvature can be formed on the top surface12300 of this cone-shape lens to achieve optical focusing orconcentration. In other embodiments, the top surface of this cone-shapedlens can also have aspheric surface curvature or any other shape toachieve optical beam focusing or concentration. An aspheric top surface12300 is used to achieve light collimation or concentration. The topsurface 12300 is coated with anti-reflection coating(s) and the surfacereflection is substantially zero. In some other embodiments, the topsurface may also not be coated with any anti-reflection coating orcoated with other coating to achieve different surface reflections.

The simulated optical flux distribution at a surface that is 5 metersaway is shown in FIG. 12B. The simulation shows that at 5 meters awayfrom the light source, most of optical power that is originally emittedfrom the light emitter 12100 is concentrated into a circular area with adiameter of 200 cm. In other embodiments, other focusing optical devicecan also be used. In addition, focusing optical devices with differentfocal lengths can be chosen to achieve different light output beamangles.

The cone mirror's slope angle (also referred to as half-cone angle),θ_(half-cone) is chosen to satisfy two conditions. First condition isthat there is only one reflection or no reflection by the cone mirror toany optical beam emitted by the light emitter. Second condition is thatall of the light exiting the top opening of the cone mirror can becollimated or concentrated by the optical focusing device withoutoptical beam cut-off. The condition 1 can be explained using FIG. 13. InFIG. 13, The light emitter 13100 is a point source and has a broademission pattern. The height of the cone mirror 13200 is much largerthan the light emitter dimension. Assuming that one light beam has ahalf beam angle of θ_(half-beam), the light beam will be reflected bythe cone mirror surface with slope angle of θ_(half-cone). The reflectedbeam will have a half beam angle of

θ′_(half-beam)=θ_(half-beam)−2×θ_(half-cone)  (3).

The lower limit of the cone mirror slope angle, θ_(half-cone), should bechosen in a way that reflected beam has half beam angle no larger thanthe cone mirror slope angle itself so that there is no second reflectionfrom cone mirror 13100. For a light emitter's light emission patternwith largest beam angle of 180°, (largest half beam angle isθ_(half-beam)=90°), the smallest cone mirror slope angle should be aboutθ_(half-cone)=30°.

The upper limit of the cone mirror slope angle, θ_(half-cone) isdetermined by the focusing optical device at the top opening of the conemirror. Most of the focusing optical device, such as collimation lens,has a numerical aperture, much less than 1. Any light beam locatedoutside the numeric aperture of the focusing optical device will not becollimated by the device. For example, if the numerical aperture of thefocusing optical device is NA=0.6, the beam angle of the light exitingthe cone mirror top opening should be no larger than 74°. The lightemission exiting the cone mirror top opening has a beam angle similar tothe cone mirror's cone angle. Therefore, the cone mirror's slope angle,θ_(half-cone), should be no larger about 37°. If the numerical apertureof the focusing optical device is NA=0.7, the beam angle of the lightexiting the cone mirror top opening should be no larger than about 90°.The cone mirror's slope angle, θ_(half-cone), should be no larger about45°.

Similarly, the upper limit of the sidewall slope angle for collimationlens, as shown in FIG. 7A, is decided by the numerical aperture of thetop curved surface. If the numerical aperture of the top curved surfaceis NA=0.6, the cone-shape sidewall of the lens should have a slopeangle, θ_(half-cone), no larger about 37°. If the numerical aperture ofthe top curved surface is NA=0.7, the cone-shape sidewall of the lensshould have a slope angle, θ_(half-cone), no larger about 45°.

In one embodiment, the light emitter can include any device or componentthat has a surface to emit the light in multiple directions with broadangular distribution patterns. The possible choices are, but not limitedto, LED chip, LED lamp, packaged LED emitter, light bulb, filament thatemits light, plasma that is confined in a certain volume, light emittingsurfaces from light-guides, light emitting surfaces from a waveguide(s),light emitting surfaces from fibers or a fiber bundle(s), and any objectthat can emit light at any spectrum. In addition, single emitting deviceor a group of multiple emitting devices can be included in the lightemitter. Light emitter can also have single or multiple lightembittering elements, such as that one LED emitter can have single LEDchip or an array of multiple LED chips, to contribute to the totalemission from the light emitter. The emitter emission surface can besmaller, larger, or equal to the diameter of the cone mirror base. Theemission surface in which light emission enters the cone mirror throughthe base opening is the effective emission surface of the emitter. Tomaximize light emission entering the cone mirror, the emitter is placedat the cone mirror base, or as close as possible to the cone mirror baseopening.

The light emitter used in the light source fabrication is not limited tothe emitters shown in the above examples. Other possible light emitterscan be used, as long as the optical emission from the emitter can enterthe cone mirror base. For example, the light emitter with a dome-shapedsurface, light emitter with a conical surface, light emitter with aroughed surface, light emitter with a surface having an arbitrarymorphology, or a light emitter with an irregular or regular surface canbe used in the directional light source fabrication. Also, multiplelight emitters or multiple light emitting devices located near or at thebase of the cone mirror can be used for this directional light sourcefabrication. Light emitters with rectangular shapes, polygonal shapes,or any other shapes can be used as a light emitter for this directionallight source fabrication, as long as the light emission can enter thecone mirror from the base.

Also, there is no limitation of the color or spectrum of the emittedlight from the emitter. The light emitter chosen in this directionallight source, can be single color or single wavelength light emitter, orcan be broad spectrum, such as white light emitter. It can also be thecombination of several single color emitting devices. Additionally, thelight emitter can emit coherent light or can also emit incoherent light.To achieve a virtual-point light source, the gap between the emissionsurface of the emitter and the edge of cone mirror base opening, and/orthe gap between the multiple emitting devices if more than one emitterinside the cone mirror base, is substantially small. Therefore, theconcentrated or collimated optical flux distribution on the illuminatedarea is substantially uniform.

The optical focusing device used in this directional light sourcefabrication, can be any focusing device, such as a bi-convex sphericallens, plano-convex spherical lens, bi-convex aspheric lens, plano-convexaspheric lens, Fresnel lens, binary lens, gradient-index lens, sphericalinterface between different media, aspheric interface between differentmedia. Also, the surface curvature of the optical focusing device is notlimited, as long as it provides proper effective focal length to matchthe light source design need. Optical focusing device with roughedsurface, such as aspheric lens with scattering surface, can also beused. The optical focusing device is big enough so that all of the lightoutput from the cone mirror opening can be collected by it. In someembodiments, different optical focusing devices may cause differentoptical aberrations. As a result, the beam angle and the angulardistribution of collimated or concentrated beam may vary, depending onthe optical focusing device to be used. For example, an aspheric lenscan have a good collimation function on point-like source, while aspherical lens has significant optical aberration for collimation. As aresult, a directional light source using an aspheric lens can have asmaller output beam angle compared to a spherical lens.

In one embodiment, a light engine is introduced. The light enginecomprises a light emitter emitting light and a cone-shaped mirror havinga base opening. The light emitter is disposed at the base opening. Oneor more first reflection images of the light emitter result from firstreflection of the light off the cone-shaped mirror. The light emitteroccupies a substantial portion of the base opening so that the lightemitter and the first reflection images form a virtual point lightsource with minimal gap(s) or without any gap between the light emitterand the first reflection images. The cone-shaped mirror has a half-coneangle from about 30 degrees to 45 degrees.

In a related embodiment, the cone-shaped mirror has a height at leastthree times more than a diameter of the base opening. In another relatedembodiment, the light emitter includes at least one light emitting diode(LED). In another related embodiment, light emitted from a top openingof the cone-shaped mirror has a beam angle no larger than 90 degrees. Inanother related embodiment, the cone-shaped mirror has a horizontalcross-section with a circular shape or a polygonal shape or an ovalshape or a rectangular shape or a triangular shape. In another relatedembodiment, the cone-shaped mirror has a top opening with a shapedifferent from a shape of the bottom opening.

In another related embodiment, the cone-shaped mirror has a reflectiveinside surface. In another related embodiment, the cone-shaped mirrorhas a height at least five times more than a diameter of the baseopening. In another related embodiment, the cone-shaped mirror has aheight at least eight times more than a diameter of the base opening. Inanother related embodiment, a beam angle of the light engine θ_(beam) isdetermined by

θ_(beam)=2×tan⁻¹[(h×tan (θ_(cone)/2)×a)/h];

wherein θ_(cone) is a cone angle of the cone-shaped mirror, h is aheight of the cone-shaped mirror, and a is a diameter of the baseopening of the cone-shaped mirror. In another related embodiment, thecone-shaped mirror further has a reflective inside surface, a topopening, and an axis passing through a center of the base opening and acenter of the top opening, and the intersection of any plane containingthe axis and the reflective inside surface has a profile with a constantslope.

In another embodiment, an apparatus is introduced. The apparatuscomprises: a cone-shaped mirror having a top opening and a base opening,wherein the base opening is the light receiving end and the top openingis the light exiting end; and a focusing optical device opticallycoupled to the cone-shaped mirror, wherein substantially all lightexiting from the top opening of the cone-shaped mirror reaches thefocusing optical device.

In a related embodiment, the cone-shaped mirror has a half-cone angle ofat least 30 degrees. In another related embodiment, the cone-shapedmirror has a height at least three times more than a diameter of thebase opening. In another related embodiment, the cone-shaped minor has aheight at least five times more than a diameter of the base opening. Inanother related embodiment, the cone-shaped mirror has a height at leasteight times more than a diameter of the base opening. In another relatedembodiment, the cone-shaped mirror has a horizontal cross-section with acircular shape or a polygonal shape or an oval shape or a rectangularshape or a triangular shape. In another related embodiment, the topopening has a shape different from a shape of the bottom opening. Inanother related embodiment, the focusing optical device is configured sothat light emitted from the focusing optical device has a beam angle ofless than 15 degrees. In another related embodiment, the focusingoptical device has a surface coated with an anti-reflection coating. Inanother related embodiment, the focusing optical device is disposed inclose proximity of the top opening of the cone-shaped mirror. In anotherrelated embodiment, the focusing optical device is disposed in adistance from the top opening of the cone-shaped mirror. In anotherrelated embodiment, the focusing optical device includes a bi-convexspherical lens, a plano-convex spherical lens, a concave-convex lens, abi-convex aspheric lens, a plano-convex aspheric lens, a Fresnel lens, abinary lens, a gradient-index lens, a spherical interface betweendifferent media, or an aspheric interface between different media. Inanother related embodiment, the cone-shaped mirror further has areflective inside surface and an axis passing through a center of thebase opening and a center of the top opening, and the intersection ofany plane containing the axis and the reflective inside surface has aprofile with a constant slope. In another related embodiment, thecone-shaped mirror has a half-cone angle of less than or equal to 45degrees.

In another embodiment, a light engine is introduced. The light enginecomprises: a light emitter emitting light; a cone-shaped mirror having abase opening, wherein one or more first reflection images of the lightemitter result from first reflection of the light off the cone-shapedmirror, and wherein a height of the cone-shaped mirror is at least threetimes more than a diameter of the base opening; and a focusing opticaldevice optically coupled to the cone-shaped mirror, whereinsubstantially all light exiting from the top opening of the cone-shapedmirror reaches the focusing optical device. The light emitter occupies asubstantial portion of the base opening so that the light emitter andthe first reflection images form a virtual point light source withminimal gap(s) between the light emitter and the first reflectionimages.

In a related embodiment, wherein the cone-shaped mirror has a half-coneangle of at least 30 degrees. In another related embodiment, the lightemitter includes at least one light emitting diode (LED). In anotherrelated embodiment, the cone-shaped mirror has a half-cone angle of lessthan or equal to 45 degrees. In another related embodiment, thecone-shaped mirror has a top opening with a shape different than thebottom opening shape. In another related embodiment, the cone-shapedmirror has a horizontal cross-section with an asymmetric shape. Inanother related embodiment, the cone-shaped mirror has a horizontalcross-section with a circular shape or a polygonal shape or an ovalshape or a rectangular shape or a triangular shape. In another relatedembodiment, the focusing optical device has a focus in close proximityof the light emitter. In another related embodiment, the smallestpossible beam angle of the light engine θ_(beam) is determined by

θ_(beam)=2×tan⁻¹ [H′/(2s′)]=2×tan⁻¹ [H/(2s)];

wherein H is a diameter of the virtual point light source, s is adistance between the virtual point light source and the focusing opticaldevice, H′ is a diameter of an image of the virtual point light sourceformed by light traveling through the focusing optical device, and s′ isa distance between the image of the virtual point light source and thefocusing optical device. In another related embodiment, the cone-shapedmirror has an axis passing through a center of the base opening and acenter of a top opening of the cone-shaped mirror, and the intersectionof any plane containing the axis and the reflective inside surface has aprofile with a constant slope.

In another embodiment, a collimation lens for collimating a light isintroduced. The collimation lens comprises: a transparent opticalmaterial; a base surface having a diameter to receive the light; acone-shaped sidewall to reflect a portion of the light; and a curved topsurface through which the light travels out of the collimation lens. Thecollimation lens has a height of the cone shaped sidewall at least threetimes larger than the diameter of the base surface.

In a related embodiment, the curved top surface has a focus in closeproximity of a center of the base surface. In another relatedembodiment, the height of the cone-shaped sidewall is at least fivetimes larger than the diameter of the base surface. In another relatedembodiment, the height of the cone-shaped sidewall is at least eighttimes larger than the diameter of the base surface. In another relatedembodiment, comprising a reflective coating coated on at least a portionof the cone-shaped sidewall. In another related embodiment, the basesurface is a flat surface. In another related embodiment, the basesurface is a concave semi-spherical surface. In another relatedembodiment, a horizontal cross-section of the cone-shaped sidewall has acircular shape or a polygonal shape or an oval shape or a rectangularshape or a triangular shape. In another related embodiment, a boundaryof the curved top surface has a different shape than a shape of aboundary of the base surface. In another related embodiment, thecollimation lens further comprises an anti-reflection coating coated atthe base surface and/or the curved top surface. In another relatedembodiment, the curved top surface has a spherical curvature, anaspheric curvature, or a Fresnel surface. In another related embodiment,the collimation lens further comprises an axis passing through a centerof the base surface and a center of the curved top surface, and theintersection of any plane containing the axis and the cone-shapedsidewall has a profile with a constant slope. In another relatedembodiment, the cone-shaped sidewall has a half-cone angle of at least30 degrees. In another related embodiment, the cone-shaped sidewall hasa half-cone angle of less than 45 degrees.

In another related embodiment, a light engine is introduced. The lightengine comprises the collimation lens and a light emitter emitting lightinto the collimation lens. The light emitter is optically coupled to anddisposed in close proximity to the base surface. One or more firstreflection images of the light emitter result from first reflection ofthe light off the cone-shaped sidewall. The light emitter and the firstreflection images form a virtual point light source with minimal gap(s)or without gap between the light emitter and the first reflectionimages.

In another embodiment, a light engine is introduced. The light enginecomprises a light emitter emitting light and a collimation lens. Thecollimation lens has a cone-shaped sidewall, a base surface and a curvedtop surface. The height of the cone-shaped sidewall is at least threetimes more than the diameter of the base surface. The light emitter isoptically coupled to and disposed in close proximity to the basesurface. One or more first reflection images of the light emitter resultfrom first reflection of the light off a surface of the cone-shapedsidewall. The diameter of the light emitter is substantially close tothe diameter of the base surface so that the light emitter and the firstreflection images form a virtual point light source with minimal gap(s)or without any gap between the light emitter and the first reflectionimages.

While the principles of the invention have been described herein, it isto be understood by those skilled in the art that this description ismade only by way of example and not as a limitation as to the scope ofthe invention. For example, a cone mirror or cone-shaped collimationlens with any cross-sectional shape may be utilized to form adirectional virtual point source and are understood to be within thescope of the invention. Reference numerals corresponding to theembodiments described herein may be provided in the following claims asa means of convenient reference to the examples of the claimed subjectmatter shown in the drawings. It is to be understood however, that thereference numerals are not intended to limit the scope of the claims.Other embodiments are contemplated within the scope of the presentinvention in addition to the exemplary embodiments shown and describedherein. Modifications and substitutions by one of ordinary skill in theart are considered to be within the scope of the present invention,which is not to be limited except by the recitations of the followingclaims.

What is claimed is:
 1. A collimation lens for collimating a light,comprising: a transparent optical material; a base surface having adiameter to receive the light; a cone-shaped sidewall to reflect aportion of the light; and a curved top surface through which the lighttravels out of the collimation lens; wherein the collimation lens has aheight of the cone shaped sidewall at least three times larger than thediameter of the base surface.
 2. The collimation lens of claim 1,wherein the curved top surface has a focus in close proximity of acenter of the base surface.
 3. The collimation lens of claim 1, whereinthe height of the cone-shaped sidewall is at least five times lamer thanthe diameter of the base surface.
 4. The collimation lens of claim 1,wherein the height of the cone-shaped sidewall is at least eight timeslarger than the diameter of the base surface.
 5. The collimation lens ofclaim 1, further comprising a reflective coating coated on at least aportion of the cone-shaped sidewall.
 6. The collimation lens of claim 1,wherein the base surface is a flat surface.
 7. The collimation lens ofclaim 1, wherein the base surface is a concave semi-spherical surface.8. The collimation lens of claim 1, wherein a horizontal cross-sectionof the cone-shaped sidewall has a circular shape, a polygonal shape, anoval shape, a rectangular shape or a triangular shape.
 9. Thecollimation lens of claim 1, wherein a boundary of the curved topsurface has a different shape than a shape of a boundary of the basesurface.
 10. The collimation lens of claim 1, further comprising ananti-reflection coating coated at the base surface and/or the curved topsurface.
 11. The collimation lens of claim 1, wherein the curved topsurface has a spherical curvature, an aspheric curvature, or a Fresnelsurface.
 12. The collimation lens of claim 1, wherein the collimationlens further comprises an axis passing through a center of the basesurface and a center of the curved top surface, and the intersection ofany plane containing the axis and the cone-shaped sidewall has a profilewith a constant slope.
 13. The collimation lens of claim 1, wherein thecone-shaped sidewall has a half-cone angle of at least 30 degrees. 14.The collimation lens of claim 1, wherein the cone-shaped sidewall has ahalf-cone angle of less than 45 degrees.
 15. A light engine, comprising:a collimation lens of claim 1; and a light emitter emitting light intothe collimation lens, the light emitter being optically coupled to anddisposed in close proximity to the base surface; wherein one or morefirst reflection images of the light emitter result from firstreflection of the light off the cone-shaped sidewall; and wherein thelight emitter and the first reflection images form a virtual point lightsource with minimal gap(s) or without gap between the light emitter andthe first reflection images.
 16. A light engine, comprising: a lightemitter emitting light; and a collimation lens having a cone-shapedsidewall, a base surface and a curved top surface, wherein a height ofthe cone-shaped sidewall is at least three times more than a diameter ofthe base surface, and the light emitter is optically coupled to anddisposed in close proximity to the base surface; wherein one or morefirst reflection images of the light emitter result from firstreflection of the light off a surface of the cone-shaped sidewall, and adiameter of the light emitter is substantially close to the diameter ofthe base surface so that the light emitter and the first reflectionimages form a virtual point light source with minimal gap(s) or withoutany gap between the light emitter and the first reflection images. 17.The light engine of claim 16, wherein the curved top surface has a focusin close proximity of a center of the base surface.
 18. The light engineof claim 16, wherein the height of the cone-shaped sidewall is at leastfive times larger than the diameter of the base surface.
 19. The lightengine of claim 16, wherein the height of the cone-shaped sidewall is atleast eight times larger than the diameter of the base surface.
 20. Thelight engine of claim 16, further comprising a reflective coating coatedon at least a portion of the cone-shaped sidewall.
 21. The light engineof claim 16, wherein a horizontal cross-section of the cone-shapedsidewall has a circular shape, a polygonal shape, an oval shape, arectangular shape or a triangular shape.
 22. The light engine of claim16, wherein a boundary of the curved top surface has a different shapethan a shape of a boundary of the base surface.
 23. The light engine ofclaim 16, further comprising an anti-reflection coating coated at thebase surface and/or the curved top surface.
 24. The light engine ofclaim 16, wherein the curved top surface has a spherical curvature, anaspheric curvature, or a Fresnel surface.
 25. The light engine of claim16, wherein the collimation lens further comprises an axis passingthrough a center of the base surface and a center of the curved topsurface, and the intersection of any plane containing the axis and thecone-shaped sidewall has a profile with a constant slope.
 26. The lightengine of claim 16, wherein the cone-shaped sidewall has a half-coneangle of at least 30 degrees.
 27. The light engine of claim 16, whereinthe cone-shaped sidewall has a half-cone angle of less than 45 degrees.28. The light engine of claim 16, wherein the light emitter includes atleast one light emitting diode (LED).